A conventional trampoline generally includes a trampoline frame to support a jumping mesh. The trampoline frame is constructed by assembling a plurality of support means. For instance, China patent No. CN2806855 discloses an improved weldless connection apparatus that includes a transverse connection tube and a longitudinal connection tube that cross each other to form a T-shaped structure. The transverse connection tube includes two opposing walls each includes an anchor hole formed thereon. During implementation a plurality of the weldless connection apparatus are connected to a trampoline frame, then a plurality of springs are connected to a rebounding surface located in the trampoline frame. The trampoline frame consists of a plurality of arched tubes. The transverse connection tube is inserted by two arched tubes. One of the arched tubes further passes through another arched tube. The two arched tubes include respectively a hole corresponding to the anchor hole that are fastened together via a connector to anchor any two arched tubes of the trampoline frame without falling apart due to stretching of the rebounding surface and the springs.
However, when users are jumping on the rebounding surface on jumping exercise, because there is no any protection measure around the trampoline frame, the users could rebound outside the trampoline frame and fall to the floor. To remedy such a problem Applicant has proposed an improvement of adding a protection encircled mesh disclosed in China patent No. CN202237001. It is a trampoline equipped with a protection encircled mesh. The trampoline includes a frame, a jumping portion, a reinforced connection portion and a protection encircled mesh. The frame includes an annular base rack, a plurality of support racks installed on the annular base rack and an encircled mesh support rack assembly installed on the support racks. The protection encircled mesh is connected to an inner side of the encircled mesh support rack assembly. Through the protection encircled mesh users can be protected from falling outside of the trampoline during rebounding from the jumping portion.
However, on CN202237001 the encircled mesh support rack assembly is anchored on the outer side of the support racks through screw fastening. The encircled mesh support rack assembly still is prone to loosening from the support racks due to stress or other factors generated by jumping of the users. To resolve the aforesaid problem another China patent No. CN201250829 discloses a trampoline frame tube connection structure which includes two frame tubes, a leg tube, a protection fence tube and a connection element. The connection element includes a longitudinal tube, a transverse tube welded to the longitudinal tube, a reinforced tube located in the transverse tube and exposed outside thereof, and a fastening hole located on the transverse tube communicating with the reinforced tube. During implementation of the trampoline frame tube connection structure the two frame tubes inserted into two opposing sides of the transverse tube, the protection fence tube runs through the reinforced tube, and the fastening hole is screwed via a screw to fasten the frame tubes and the protection fences tube, thereby enhance the structural strength between the protection fence tube and the connection element from loosening caused by shaking and vibration of the trampoline.
However, on CN201250829, although the trampoline frame connection structure has tried to overcome the loosening problem through mutual fastening of the transverse tube, the frame tube and the protection fence tube, the two frame tubes merely are supported by the transverse tube without one frame tube passing through another frame tube, and the leg tube and the protection fence tube also do not couple with each other. As a result, the two frame tubes, the leg tube and the protection fence tube are easily bent due to vibration of the trampoline or during transportation. In addition, because the transverse tube, the frame tube and the protection fence tube are fastened via a screw, the screw could fracture when subject to excessive stress during jumping and rebounding process of the users. Hence how to design a support structure to overcome the problem of inadequate structural strength that occurs to the conventional techniques is an issue yet to be resolved